Tiny black crystal of the extremely rare Lengenbach minerals stalderite-ralphcannonite (this one, new species: IMA 2014-077) in a small matrix of realgar. Stalderite and ralphcannonite form a series, where stalderite is the Cu-end member and ralphcannonite is the Ag-end member. This crystal was analyzed by EDX and it is stalderite (61%) and ralphcannonite (39%). In addition, this specimen is a part of the type specimen of ralphcannonite (!), that is, the specimen that was used for the description of the species! Only very few specimens known of both species. After the book "Faszination Lengenbach (2008)" we know that the total number of stalderite specimens known was only 9! Specimen found in 1989. — Photo: David Hospital · CC BY-SA 4.0
Stalderite
Stalderite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula TlCu(Zn,Fe,Hg)₂As₂S₆.
It crystallizes in the tetragonal crystal system (space group I-42m). It is a member of the Routhierite structural group.
IMA symbol Sld, IMA status: approved, named in 1987.
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